Steve Mallet posted an interesting piece on the limits of community: <=150 people. I played around with this number, wondering what relationship it might have to the well-known six degrees of separation. If I know 150 people and each of those know another 100 that I don't know, and so on, does that "explain" six degrees of separation?

Of course, these are stupid silly numbers, but I calculated that if about 62% of my contacts' contacts are people not already on my contact list, then within six degrees of separation I've got the whole world covered.